Study: More 9.0 Magnitude or Stronger Mega Earthquakes Are Coming

Increasing numbers of typhoons aren’t going to be the only natural disasters mankind will have to expect and prepare for. Scientists writing in the Bulletin of the Seismological Study of America are anticipating mega earthquakes to happen soon as the Pacific’s earthquake zones are expected to have have come full circle in their 10,000 year cycle. Researchers are saying that it will not be surprising to experience magnitude 9.0 or stronger earthquakes near the Pacific Ocean’s volcanic “Ring of Fire” in the coming months or years.

The research is titled “Magnitude Limits of Subduction Zone Earthquakes.” It is co-authored by Yufang Rong and Harold Magistrale of FM Global’s Center for Property Risk Solutions, David Jackson of the University of California – Los Angeles, and Chris Goldfinger of Oregon State University. This research paper was first published online by the Bulletin of the Seismological Study of America (BSSA) and will be available in print on the October issue.

Simulations from Historical Seismic Data

The researchers led by Yufang Rong have come up with their mega earthquake predictions after running computerized Monte Carlo simulations based on historical data for seismic activity in subduction zones around the Pacific. These simulations allowed them to establish estimates of the maximum earthquake magnitudes that can be expected over various time spans.

Details of the simulation results have been presented in a September 15 news release on EurekAlert!. Aside from the 10,000-year estimated cycle of 9.0 magnitude earthquakes, the research team also reckoned that slightly less powerful earthquakes at 8.5 magnitude can be expected every 250 years while 8.8 magnitude quakes are expected to occur every half a century.

What Is Maximum Magnitude?

The term “maximum magnitude” is quite prominent in the published research. So what does it mean? How is it different from the ordinary “magnitude?” Maximum magnitude is a vital parameter in calculating seismic hazard. In simple terms, it is the likely size of an earthquake that has not yet occurred in the area being studied. It has a value that is higher than the historical highest quake magnitude to have struck an area. Rong emphasized that as of now it is still not possible to know the exact value of maximum magnitude. The numbers they presented in their research were based on a simple methodology that estimates maximum magnitude within a specific time frame.

The researchers, however, cautioned that the figures they came up with cannot be considered as forecasts similar to the forecasts on weather conditions. Yufang Rong said that these numbers are mere estimates or probabilities based on statistical distribution. Until now, scientists still haven’t been able to come up with the technology, methodology, or device that is capable of forecasting or predicting seismic activity, let alone the occurrence of mega earthquakes. Rong adds that “just because a subduction zone hasn’t produced a magnitude 8.8 in 499 years, that doesn’t mean one will happen next year.”

Not Applicable to Seismic Faults on Land

It is important to emphasize that these estimates don’t cover land-based seismic. They are only based on underwater faults. The magnitude 6.0 quake in Napa, California a month ago is not a part of the expected quakes under the 250-year, 500-year, and 10,000-year estimated cycles. Likewise, these estimates cannot be used to predict seismic activity risks in the San Andreas Fault. However, they can be used to anticipate quakes at the Cascadia subduction zone off the coast of Washington. Back in 1700, this subduction zone was reported to have experienced a magnitude 9.0 quake that manifested as gigantic tsunamis on the Japanese coasts.

By Leohotens [Public domain], via Wikimedia Commons

Pacific Northwest Seismic Network director John Vidale said in an interview with NBC News that the recently published research was “pretty much in line” with what he and his group are anticipating from subduction zone in Cascadia. He said that “a 9 every 500 to 1,000 years is already about what we expect in Cascadia.” Vidale believes that the traditional way of earthquake-proofing structures may have to change as earthquakes become expected but are still going to be unexpected.

Major quakes are “expected” in the sense that several studies are already in agreement that powerful earthquakes are going to happen soon but they are still “unexpected” because, still, nobody has the technology or methodology to know exactly (or even at a year-bound estimate) when and where the quakes will occur.